1,1-Dichlorotetrafluoroethane
Chemical compound
From Wikipedia, the free encyclopedia
1,1-Dichlorotetrafluoroethane is a chlorofluorocarbon also known as CFC-114a or R114a by American Society of Heating, Refrigerating, and Air Conditioning Engineers.[2] It has two chlorine atoms on one carbon atom and none on the other. It is one of two isomers of dichlorotetrafluoroethane, the other being 1,2-dichlorotetrafluoroethane, also known as CFC-114.
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| Names | |
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| Preferred IUPAC name
1,1-Dichloro-1,2,2,2-tetrafluoroethane | |
| Other names
R114a; CFC-114a | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.006.159 |
| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C2Cl2F4 | |
| Molar mass | 170.92 g·molâ1 |
| Density | 1.455 g/cu cm (as a liquid under pressure) |
| Melting point | â56.6 °C (â69.9 °F; 216.6 K) |
| Boiling point | 3.4 °C (38.1 °F; 276.5 K) |
| 137 mg/L | |
| Solubility | benzene, diethyl ether, ethanol |
| log P | 2.78 |
| Vapor pressure | 1640 mm Hg |
Refractive index (nD) |
1.3092 at 0 °C |
| Hazards | |
| GHS labelling:[1] | |
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| Danger | |
| H335, H336, H370, H420 | |
| P260, P264, P270, P271, P304+P340, P308+P316, P319, P321, P403+P233, P405, P501, P502 | |
| Related compounds | |
Related compounds |
CFC-114 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Formation
1,1-Dichlorotetrafluoroethane can be made free from other isomers by reacting trichlorotrifluoroethane (CFC-113 or CFC-113a) with antimony pentachloride.[3] Trichlorotrifluoroethane can also be reacted with sulfur tetrafluoride or dichlorodifluoromethane with aluminium fluoride catalyst to yield 1,1-dichlorotetrafluoroethane. The use of aluminium in the catalyst favours the asymmetric molecules.[4]
It can also be made in a reaction of tetrachloroethylene with hydrogen fluoride and chlorine, but this results in a mixture.[3]
Fluorinating 1,2-dichlorodifluoroethylene with fluorine produces a small amount of 1,1-dichlorotetrafluoroethane, but mostly tetrachlorotetrafluorobutene and some other chloroflurocarbons, so is not a good way.[5]
Properties
1,1-Dichlorotetrafluoroethane has a close boiling point (3.6°C) to the isomer 1,2-dichlorotetrafluoroethane (3.8°C), and so is difficult to separate by distillation.[6] Also in a gas chromatograph, it is hard to distinguish from the symmetric 1,2 isomer.[6]
Critical properties include critical temperature 145.7°C, critical pressure 4.92 MPa and critical density of 0.82 g/ml.[7]
1,1-Dichlorotetrafluoroethane does not ignite in air.[7]
Reactions
1,1-Dichlorotetrafluoroethane reacts with hydrogen when heated at 300 to 600°C with a palladium catalyst in a hydrodechlorination. The main reaction product is 1,1,1,2-tetrafluoroethane, but also 1-chloro-1,2,2,2-tetrafluoroethane (CF3CHClF) and 1,1,1-trifluoroethane are formed.[8]
1,1-Dichlorotetrafluoroethane reacts with alkali metals, alkaline earths and aluminium.[7]
When heated with hydrogen over a nickel catalyst, 1,1-dichlorotetrafluoroethane is dechlorinated with replacement by hydrogen to yield a mixture of CF3CHClF and the dimer CF3CClFCClFCF3.[9]
Use
CFC-114a was used in aerosol propellants, blowing agents, and in polyolefin foams. There was also use in refrigerants. Production was banned in by the Montreal Protocol.[10]
CFC-114a is a possible intermediate in the production of HFC-134a[10] which can be produced by hydrogenation.[11]
Atmosphere
The ozone depletion potential of 1,1-dichlorotetrafluoroethane is 0.72.[12] The estimated lifetime in the atmosphere is about 100 years.[12] The radiative efficiency is 0.28 Wmâ2ppbâ1.[12] Global warming potential in 20 years is 6750.[12] The atmospheric concentration of CFC-114a is not usually measured separately from CFC-114 due to difficulties in distinguishing them apart.[12]
In 1978 atmospheric levels of CFC-114a were 0.35 ppt. By 2020 the level was up to 1.13â¯ppt.[13] CFC-114a appears to be emitted into the atmosphere is South East Asia.[10]
The atmospheric natural destruction of CFC-114a is by reaction with atomic oxygen, or breakup by ultraviolet light.[10] As of 2014 about 250 tons per year of CFC-114a were being put into the atmosphere.[10]